Effect of CCC and daminozide on growth of silver birch container seedlings during three years after spraying

Applications of growth retardants, daminozide and CCC (chlormequatchloride), were studied in order to determine their effects on morphology and post-planting growth of silver birch (Betula pendula Roth) container seedlings. Daminozide was sprayed once (on 28 June at concentrations of 1.0 – 6.0 g l−1) and CCC was sprayed twice (on 29 June and 27 July at concentrations of 0.5–3.0 gl−1). Height growth, morphology of seedlings at the end of the growing season, the shoot and root growth potential the following spring and field performance during the following seasons were measured. During the first summer in the nursery, both daminozide and CCC retarded height growth,but daminozide was more effective. The effects of compounds on stem diameter during the summer of application were small. Neither of the compounds affected the field performance of seedlings. The most suitable applications for retardation of height growth, without negative effects on other morphological variables, were 4 g l−1 (32 mg per seedling) for daminozide and 2 g l−1 (16 mg per seedling), sprayed in two applications, for CCC.